They didn't do anything wrong. But users are left with massive Python 2 codebases (certbot/letsencrypt, caldav-server/twisted, blender, maybe some OpenStack stuff and probably much more) that are very useful/essential to their users. What do you expect mere users to do? Invest massively in porting (adding test cases in the process where there don't exist any)? They will rather keep Python 2 around forever.
I wouldn't be surprised if Blender was dragging their feet moving to Python 3 just because all of the major 3d software tools have embedded Pythons that are only recently reaching 2.7 (Maya, Nuke, Houdini, Mari, etc).
